In general, a vehicle is provided with an operating device to be operated by a driver, an electronic control unit for determining a target driving force of the vehicle on the basis of an operating condition of the operating device and stored data, and a drive unit adapted to generate a driving force for running the vehicle in accordance with the target driving force. An example of a vehicle in which a drive unit is controlled by an electronic control unit, that is, an example of a control device of a vehicle is disclosed by Japanese Patent Laid-Open No. 6-146951. According to the throttle valve control device of engine taught by Japanese Patent Laid-Open No. 6-146951, an engine is provided with a supercharger, an air intake passage, and an exhaust passage, and a throttle valve is arranged on the exhaust passage. An actuator is actuated in accordance with a control signal from a control unit to open and close the throttle valve. Meanwhile, a signal representing an operation quantity of an accelerator, a signal representing an engine speed, a signal representing an engine load and so on are inputted to the control unit. Accordingly, an opening degree of the throttle valve is controlled according to the engine speed, the engine load, and the operation quantity of the accelerator. For this purpose, according to the teachings of Japanese Patent Laid-Open No. 6-146951, five kinds of characteristic lines are prepared, and a value obtained by dividing a percentage of the throttle opening by a percentage of the operating quantity is different in each characteristic line. That is, the opening degree of the throttle valve is controlled by selecting one of those characteristic lines in accordance with the engine speed and the engine load. In addition, Japanese Patent Laid-Open No. 2004-182200 also discloses an invention relating to a drive unit of a vehicle.
However, according to the throttle valve control device of engine taught by Japanese Patent Laid-Open No. 6-146951, the five kinds of characteristic lines are prepared in advance in accordance with driving conditions of the vehicle, as described above. Therefore, in case of changing the characteristic line, an actual acceleration of the vehicle may be different from an expected acceleration of the driver. For this reason, the driver may feel an uncomfortable feeling about the acceleration of the vehicle.